1. Field of the Invention
The present invention relates to a method of manufacturing an outer retainer for a one-way clutch that is employed for an automatic transmission, a stator, etc of a vehicle.
2. Related Background Art
The automatic transmission etc of the vehicle involves using the one-way clutch that transmits rotary force on a driving side in one direction but does not transmit the rotary force in the opposite direction.
A conventional sprag type one-way clutch is constructed of an inner race and an outer race that are concentric and make relative rotations and of a one-way clutch mechanism interposed between the inner race and the outer race. The one-way clutch mechanism is built up by a plurality of sprags defined as torque transmitting members, a spring member that urges the sprags in an engaging direction, a cylindrical inner retainer and a cylindrical outer retainer which hold the sprags and restrain an excessive inclination thereof, and a pair of end bearings that ensure operations of the sprags by retaining these two retainers at a predetermined interval.
The outer retainer is constructed of two annular portions facing each other in an axial direction and a plurality of column members connecting these annular portions and provided at a predetermined interval in a peripheral direction. The outer retainer has a plurality of window portions configured by the column members neighboring each other and the two annular portions at a predetermined interval in the peripheral direction. Further, one annular portion is formed with an outward flange directed outward in a radial direction at an end on the opposite side to the other annular portion in the axial direction, i.e., at an end of one side of the outer retainer in the axial direction. The outward flange engages with an engagement groove formed in an inner peripheral face of the outer race, thereby positioning and supporting the outward flange with the outer race.
The inner retainer and the outer retainer have substantially the similar configuration, however, a flange formed at one end in the axial direction of the inner retainer is an inward flange directed inward in the radial direction.
In the thus-constructed one-way clutch, in the case of transmitting torque with the outer race serving as a driving race for applying rotary force to sprags, it is required to apply proper drag torque to between the outer retainer and the inner peripheral face of the outer race in order to surely transmit an operation to the sprags such as when an abrupt operation is applied to the outer race.
A known means for obtaining the drag torque is a means that forms a shaped portion called a T-bar or an i-bar in the outer retainer, gets the shaped portion deformed and thus brings the shaped portion into contact with the inner peripheral face of the outer race.
The T-bar is formed by a portion of the annular portion on the side of the outward flange cut away at two portions of the annular portion which define respectively the two window portions neighboring each other and the column member between the window portions neighboring each other. This T-bar forming means configures a T-bar defined as a T-shaped portion by the column member between the window portions neighboring each other and the divided outward flange-sided annular portion between the two cut-away portions. A plurality of thus-formed T-bars are provided at a predetermined interval, and the column members of these T-bars are bent outward in the radial direction by a predetermined quantity. In an assembled state, a scheme is that the outer retainer is held on the inner peripheral face of the outer retainer by dint of spring action of the T-bars, and the drag torque is obtained by bringing outer diametrical faces of the divided outward flanges of the plural T-bars into contact with the inner peripheral face of the outer race.
In another case, the outer retainer may be so structured that the outer diametrical faces of the divided outward flanges may engage with the engagement grooves formed in the inner peripheral face of the outer race, thus providing a mechanism for positioning the outer retainer and preventing a removal in the axial direction after being assembled. In this another structure, it is necessary to adopt a socalled i-bar structure in addition to the above T-bar structure.
The i-bar is defined as an i-shaped portion by cutting through a part of one column member, closer to the annular portion, between the neighboring window portions so as to separate the column member into two column pieces. A scheme is that a plurality of the thus-configured column members are provided at a predetermined interval, one of the separated column pieces is bent outward in the radial direction, the outer retainer is held on the inner peripheral face of the outer race by dint of spring action of these separated and bent column pieces, and these column pieces abut on the inner peripheral face of the outer race, thereby obtaining the drag torque.
Japanese Utility Model Laid-Open Publication No. 63-115637 discloses an outer retainer having a connected T-bar structure in which the T-bars are formed so as to be connected in the peripheral direction, and peripheral rigidity of the T-bar is thus improved.
The formation of the T-bar structure in the outer retainer entails, as described above, the process of cutting through a part of the annular portion on the side of the outward flange. The cutting means has hitherto adopted a method of cutting through a part of the annular portion on the side of the outward flange by a grinding stone.
Note that “Related Background Art” in the above has exemplified the T-bar, however, the operation of obtaining the drag torque is the same with a double connected T-bar in which a single window is provided between the cut-away portions or with a triple connected T-shaped bar in which two neighboring windows are provided between the cut-away portions.
In the case of the method of cutting through a part of the annular portion on the side of the outward flange by the grinding stone, however, as illustrated in FIG. 5, a burr 129 is produced in the cut-away portion even by cutting through an annular portion 103b on the side of an outward flange 109 in whichever direction. If the burr 129 remains produced in the cut-away portion, an outer retainer 101 does not fit to the inner peripheral face of an outer race 142 when assembled. Further, if the burr 129 exists in the inner peripheral direction of the outer retainer 101, the burr 129 interferes with a spring member 144, and a one-way clutch 140 undergoes a fault in operation. Accordingly, a process of removing the burr 129 is needed after the cutting process using the grinding stone in order to avoid the inconvenience described above.